We have a RAID5-SAN. There is only one huge volume where all data remains. Also the control files. When databases are created, Oracle creates 3 control files in the same directory. It doesn't matter where those files are, because when the volume fails, everything fails.

Question: Because we only have one volume, is it safe to only create two control files?

I ask this, because performance will decrease when the number of control files increase and vice versa.

Creating only one, would be best (performance wise), but I think that's a bit tricky!

A penny for your thoughts...

09-26-2003, 11:53 AM

marek_wiechula

If you have only one file system you can not very put them on two or more different file systems.

However volume failure is not the only threat. You could put them in two or more different directories and that would at least protect them from some potential accidents.

09-26-2003, 12:04 PM

efrijters

Yes, offcourse you are right. Disk corruptions are rare, but it's better to be safe than sorry.

But... if I have only two control files, stored at separate places and backup the control files regularly to a trace file, than I would have better performance because of the lower number of control files and still have good backups of them. In case of problems, you can restore the control file out of the trace file.

Originally posted by efrijters Yes, offcourse you are right. Disk corruptions are rare, but it's better to be safe than sorry.

But... if I have only two control files, stored at separate places and backup the control files regularly to a trace file, than I would have better performance because of the lower number of control files and still have good backups of them. In case of problems, you can restore the control file out of the trace file.

That script just creates a control file creation script, thats all.
Rather than using ALTER DATABASE BACKUP CONTROLFILE TO TRACE use ALTER DATABASE BACKUP CONTROLFILE TO '/absolutepath/filename.ctl'

This will copy the actual control file to the specified location.

09-26-2003, 12:21 PM

efrijters

Whoops! Okay, my mistake...

But what do you think of my idea, adewri? Is it sain or not?

09-26-2003, 12:25 PM

marist89

Re: How many control files on one volume?

Quote:

Originally posted by efrijters
Question: Because we only have one volume, is it safe to only create two control files?

Sure. However, I would put one copy of the control file on another disk even if it is local to the box.

Quote:

I ask this, because performance will decrease when the number of control files increase and vice versa. Creating only one, would be best (performance wise), but I think that's a bit tricky!

Is this a question or a statement? Any performance degradation (very little) is well worth the safety you get by putting another copy of your control file on another physical disk.

Quote:

A penny for your thoughts...

I accept paypal if that's convenient... ;)

09-26-2003, 12:32 PM

efrijters

I wasn't aware of the amount of overhead when using more/less contol files. Probably it's neglectable...

Quote:

Sure. However, I would put one copy of the control file on another disk even if it is local to the box.

The SAN has no local disks. I can ask the 'network service desk' if it is safe/possible to use a local disk of a server. (The server is in a cluster and maybe this is a problem?)

09-26-2003, 12:50 PM

marist89

Quote:

Originally posted by efrijters The SAN has no local disks. I can ask the 'network service desk' if it is safe/possible to use a local disk of a server. (The server is in a cluster and maybe this is a problem?)

Mmmm. That's a little more difficult if you're running in a cluster. I would get more disk allocated to you even if it's 10M. The danger you put yourself in with only one volume is a huge obstacle to overcome during a recovery.

09-26-2003, 01:10 PM

OracleDoc

Re: Re: How many control files on one volume?

Quote:

Is this a question or a statement? Any performance degradation (very little) is well worth the safety you get by putting another copy of your control file on another physical disk.

I've never heard of any performance degradation due to control files. The only thing that comes to my mind that would cause any degradation (if any) would be if you're using RMAN and storing RMAN's repository information in the control files. And, the only thing about that is your control files will get bigger.

Now mirroring Redo logs on a SAN enviornment now that's a different story. let the games begin.

I don't have any info on the SAN (it's a clients system), maybe I can ask them to reconfigure it ("Yes, offcourse! We'll do that right away after you explained to the customers they can't work for a few days...!")

If they could reconfigure it to multiple volumes (with multiple controllers?), then I could really mirror things... (and probably gain some performance...)

BTW: I started this thread about control files because the teacher at the Oracle University told me the theory about "multiple control files vs perfromance"...